They were politically mixed and financially battered. They cared deeply about the economy but were concerned with abortion too.

And in narrowly backing Mitt Romney, the electorate that turned out Tuesday for Michigan’s Republican presidential primary offered a snapshot of the front-runner’s strengths and weaknesses as he continues his quest to clinch the Republican nomination for president.

Romney, who was born and raised in Michigan, performed well among declared Republicans, voters with incomes above $100,000 a year, those whose top concerns were the federal deficit and the economy, and those keen on beating President Obama in the fall, according to preliminary exit polls in the state.

But he fared less well among “very conservative” voters, evangelical Christians and those who strongly support the tea-party movement — groups that have been slow to warm to the former Massachusetts governor.

Romney’s support was weaker among working-class voters, a group that was split about evenly between Romney and his chief rival Rick Santorum, who actively courted those voters. Santorum defeated him among voters who have union members in their family.

Romney also won just a slim margin of the fully 31 percent of voters who said their families had experienced a layoff in the past three years, despite his recent gaffes in talking about his wealth.

“It’s just open mouth, insert foot. Sometimes he makes comments without thinking,” said Nancy Repoz, 59, a small-business owner from Livonia.

Despite her frustration, she voted for Romney. “He appeals to the business community, and he is going to focus on creating jobs,” she said. “Santorum doesn’t have much of a business background and I think we need that business approach.”

Repoz was not alone in admiring Romney’s business credentials; 57 percent of Michigan voters rated business experience as a better indicator of effectiveness than government experience, which dominates Santorum’s résumé.

But about 14 percent of voters said that abortion was their top concern — a larger proportion than in any of the other states that have held primaries. Of those voters, 77 percent backed Santorum, who has made social issues a centerpiece of his campaign.

“Society has social issues, and someone has to talk about them,” said Nanci Burnham, 51, a church treasurer from Farmington Hills who voted for Santorum. “He’s courageous, and I don’t think he will compromise. He is a contrast to what we have now and we need that.”

In recent weeks, Romney and his supporters have been hammering the message that Santorum, who spent 15 years in Congress, is a Washington insider who often voted against his conservative values to placate party leaders. While voters said they did not like the negative advertising, many echoed the message of the anti-Santorum attack ads.

“Santorum is too much of an insider,” said Robin Whitfield, 55, a financial adviser from Livonia who considered backing the former Pennsylvania senator before settling on Romney Tuesday morning. “I understand that he was a senator, but it’s not really a job.”

Gary Spaniola, 53, a software designer from Shelby Township, said Santorum’s apparent focus on social issues was a concern because the eventual nominee will have to win over independents to beat Obama. “I was a little worried about Rick Santorum getting a little too religious,” he said.

Still, Spaniola said, his support of Romney was tenuous because of the health-care overhaul he backed in Massachusetts. “You have to send someone to Washington who knows how to run an economy, and Mitt’s the guy. But I hope he does what he says. I’m worried about him with this health-care stuff. It’s scary.”

Romney’s margin was eroded by an unknown number of Democrats who took advantage of Michigan’s open primary system, voting for Santorum in the hopes of throwing Romney off track for the nomination. About 9 percent of primary-goers Tuesday identified themselves as Democrats, according to exit polls, and over half of those cast their ballots for Santorum. The remainder were split between Romney and Rep. Ron Paul.

Paul also complicated matters for Romney, winning 22 percent of independents and faring well among young voters. But it is unclear whether those voters would have backed either Romney or Santorum had Paul stayed out of the race. More than a third of Paul supporters said they will not vote Republican in November unless the Texas congressman is the nominee.

Newt Gingrich, who did not compete in the state, may have drawn support away from Santorum, given his support among many of the same groups that preferred Santorum.

Sandhya Somashekhar is the social change reporter for the Washington Post.

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